diff --git a/docs/.vitepress/theme/components/VocabQuiz.vue b/docs/.vitepress/theme/components/VocabQuiz.vue
index 2e41078..6a15af9 100644
--- a/docs/.vitepress/theme/components/VocabQuiz.vue
+++ b/docs/.vitepress/theme/components/VocabQuiz.vue
@@ -67,13 +67,23 @@
           <div v-else v-html="v.notes"></div>
         </blockquote>
         <div v-if="example">
-          <blockquote
-            v-if="exNotes"
-            v-html="markdownIt.render(exNotes)"
-          ></blockquote>
-          <button type="button" v-else @click="explainSentence(example.ko)">
-            Explain sentence
-          </button>
+          <div v-if="exNotes">
+            <button
+              type="button"
+              @click="
+                exNotes = '';
+                explainSentence(example.ko);
+              "
+            >
+              New explanation
+            </button>
+            <blockquote v-html="markdownIt.render(exNotes)" />
+          </div>
+          <div v-else>
+            <button type="button" @click="explainSentence(example.ko)">
+              Explain sentence
+            </button>
+          </div>
         </div>
       </details>
     </nav>
@@ -168,7 +178,7 @@ const vaud = useTemplateRef<InstanceType<typeof SentenceAudio>>("vaud");
 
 const v = computed(() => vList.value[vIndex.value]);
 const example = computed(() => {
-  if (!v.value.examples?.length) return null;
+  if (!v.value?.examples?.length) return null;
   const ex = v.value.examples;
   return ex[exIndex.value];
 });
@@ -200,6 +210,25 @@ watch(quizState, () => {
   saveQuizState();
 });
 
+watch(example, () => {
+  exNotes.value = "";
+  if (!example.value) return;
+
+  if (supabase) {
+    let { ko } = example.value;
+    ko = ko.replaceAll("**", "");
+
+    supabase
+      .from("sentence-explain")
+      .select<any, { explain: string }>("explain")
+      .eq("ko", ko)
+      .then((r) => {
+        if (!r.data?.[0]) return;
+        exNotes.value = r.data[0].explain;
+      });
+  }
+});
+
 const vocabulary: Record<string, IVoc[]> = {};
 
 for (const [k, vs] of Object.entries(
@@ -400,7 +429,9 @@ const markdownIt = new MarkdownIt({
   typographer: true,
 });
 
-async function explainSentence(s: string) {
+async function explainSentence(ko: string) {
+  ko = ko.replaceAll("**", "");
+
   for await (const data of LLMstream({
     model: "deepseek-v4-flash",
     messages: [
@@ -409,14 +440,29 @@ async function explainSentence(s: string) {
         content:
           "Explain how this sentence works in 500 characters. Give key vocabularies.",
       },
-      { role: "user", content: s },
+      { role: "user", content: ko },
     ],
   })) {
-    if (data.done) return;
+    if (data.done) break;
     if (data.content) {
       exNotes.value += data.content;
     }
   }
+
+  if (supabase) {
+    console.log(supabase);
+    const user_id = await supabase.auth.getUser().then((r) => r.data.user?.id);
+    console.log(user_id);
+
+    await supabase.from("sentence-explain").upsert(
+      {
+        user_id,
+        ko,
+        explain: exNotes.value,
+      },
+      { onConflict: "ko,user_id" },
+    );
+  }
 }
 
 function onModalClickOutside(ev: MouseEvent) {
diff --git a/docs/howtostudykorean/unit-1/20-well-poorly.md b/docs/howtostudykorean/unit-1/20-well-poorly.md
index 824bf90..b579478 100644
--- a/docs/howtostudykorean/unit-1/20-well-poorly.md
+++ b/docs/howtostudykorean/unit-1/20-well-poorly.md
@@ -71,7 +71,7 @@ vocabulary:
       audio: https://www.howtostudykorean.com/wp-content/uploads/2015/11/Lesson20v6.mp3
       en: powder
       examples:
-        - ko: 케이크 반죽에 **밀가루**를 넣으세요
+        - ko: 케이크 반죽에 밀**가루**를 넣으세요
           en: Put some **flour** into the cake batter, please
         - ko: 봄에는 꽃**가루** 알레르기를 조심해 야 해요
           en: You need to be careful about **pollen** allergies in the spring